Collecting and Preserving Insects 



easily graduated by stop cocks. Rising to the height of the de- 

 flexed lip it pours in a broad cascade into the main compartment, 

 impinging on the top of the rock-work grotto. The second or 

 lower aquarium is at present similarly arranged, and derives its 

 supply of water either from the overflow of the first or independ- 

 ently from an overhead pipe, so that its water may be kept either 

 still or running at will. Thus we have arrangements in a small 



18 



Fig. 258. A good simple aquarium 



space for the rearing of all kinds of aquatic insects. The sliding 

 stream upon the artificial rockwork is particularly adapted for such 

 forms as Simulium, and opportunity is also offered for such 

 species as have the habit of crawling out either on rocks or 

 earth, as the case may be. 



400 



